Was there a time in your life when you did a selfish thing? As a baby, it is 100% of the time. No baby ever thought/said, "I am hungry, but Mom was late getting to bed last night, so I'll let her sleep in a bit and then I'll ask her to feed me".... never happens!
The Bible says that we all are motivated in our "flesh" by three basic desires: lust of the eyes, lust of the flesh and the pride of life. Lust of the eye manifests itself in the "gimme things". Gimme this, gimme that. Mine! I want the biggest piece of the pie. Lust of the flesh manifests itself in eating too much or inappropriate sensual satisfaction. Pride constitutes making a name for yourself. So, selfishness is manifest in the carrying out of these natural fleshly desires. They make one's life, "it's all about ME!" Our focus is on the ME.
This focus changes when we see and confess this sinful nature and ask Jesus, who died for us, and paid the redeeming price for us with His blood, to forgive us and come into our hearts and be the Lord of our lives. We become: born again and begin to see the Kingdom of God. We begin to see that it's not just about us but that we are a part of community, the Church, the family of God, the body of Christ! We see that Christ is the head of this body and that we compose the parts of His body. When "all the parts are working properly it makes for bodily growth and upbuilds itself in love." (Ephesians 4:16). We become body/Christ focused not me/self-focused. We move away from getting "our fair share", thinking the "the boys with the most toys win", storing up wealth so I/ME can "eat, drink and be merry". We move from that to having a present rich relationship with Jesus, caring for His body, the body of Christ, and loving the world that they might be drawn to Him, and looking for His return to take us to the heavenly City of God.
We begin to realize that because we are members of the same body what we do to bless or offend each other affects us ourselves, the other members of the same body, and Jesus who is the Head. That's why He can say, "As you did it, or did it not, to the least of these my brethren, you did it unto Me." We are all in it together. So, if we are selfish or stingy or uncaring, the whole body, including Jesus, suffers. If we are a loving, generous, blessing people, then the whole body is blessed. And if the body is blessed then it can be a blessing by being able to reach out to the unsaved world that they would be drawn to Jesus, be saved and become a part of this wonderful body, family, Church.